Auxin is a plant hormone that promotes the growth and development of the plant’s shoots. The picture below is of a small, growing plant. Auxin is being produced at the tips and forming leaves, as well as causing the plant to grow larger. It also plays important roles in the development of the embryo, phototropism, apical dominance, and fruit development. Without plant hormones such as auxin, plants wouldn’t be able to grow. The auxin could be found at the tips and meristems of this plant.